The provision of a primer composition which will adhere to numerous types of surfaces, particularly rusted iron, which will adhere to a wide variety of applied coatings, and which, at the same time is water-thinnable, presents a serious practical problem.
British Patent No. 915,512 discloses a nonaqueous primer with rust-inhibiting properties, the primer containing a phosphate of calcium or zinc as the rust inhibitor.
In U.S. Pat. No. 4,064,084, a corrosion-inhibiting coating is disclosed, but the coating must be heated to a temperature of 500.degree.-900.degree. F. to effect a cure, which is an obvious disadvantage.
U.S. Pat. No. 4,086,182 describes a composition which gives a corrosion-resistant film, but the product when applied to rusted iron or steel turns deep black in color and must be removed prior to the application of another coating since it does not adhere to a top coat.
In my prior U.S. Pat. No. 4,462,829, I disclose a highly effective rust-converting and rust-inhibiting primer but it has the disadvantage that it is not water thinnable and must be thinned with aliphatic solvents such as naphtha or mineral spirits. The primer compositions described in my prior patent have dispersing or emulsifying agents which enable dispersion of oil in water and which form a water-in-oil emulsion, but such emulsions are not water thinnable (reducible) and must be thinned by aliphatic solvents. More specifically, the film-forming resin is an alkyd resin which is present as an aqueous emulsion or aqueous suspension, but it must be thinned with aliphatic solvents or thinners which is not as environmentally clean as the water-thinnable product of this invention.